Method for preparing vapor-phase isomerization catalyst



United States Patent O 3,085,123 METHGD FOR PREPARING VAPOR-PHASEISOMERIZATION CATALYST John A. Ridgway, La Porte, Ind., and BuellOConnor, 7 Texas City, Tex., assignors to Standard Oil Company,

Chicago, 111., a corporation of Indiana N Drawing. Original applicationNov. 17, 1958, Ser. No. 774,085, now Patent No. 3,020,241, dated Feb. 6,1962. Divided and this application May 22, 1961, Ser. No. 135,687

4 Claims. (Ci. 260-68355) The present invention relates to a method forpreparing a vapor-phase isomerization catalyst and, more particularly,to a method for treating a chlorine-containing, platinum-aluminareforming catalyst so as to make it highly selective and effective forthe vapor-phase isomerization of paraffins.

With the persistent rise in the octane number of motor fuels, petroleumrefiners have rapidly expanded catalytic reforming with platinumcatalyst to the point where available reforming feedstocks are beingexhausted. As a result, refiners are now turning to other processes foroctane improvement, a particularly attractive process beingisomerization. In the isomerization process, light paraffins, such asnormal pentane and normal hexane, are converted to isomers, havingsubstantially higher octane numbers, e.g., isopentane,2,2-dimethylbutane (neohexane), 2,3-dimethylbutane (diisopropyl), andthe like.

Various isomerization processes and catalysts are available, but all ofthem suffer from one or more shortcomings such as highly-corrosivecatalyst systems, relativelyloW catalyst activity, catalyst regenerationdifiiculties, costly method of catalyst preparation, and the like. Wehave now discovered a method for preparing a highlyactive isomerizationcatalyst which results in a process which is relatively free of suchdifiiculties. Our advantageous method of catalyst preparation has theadditional attribute of being able to convert a highly-active reformingcatalyst to a catalyst which is highly selective and effective forparaffin isomerization. Thus the same catalyst plant can turn out bothreforming catalyst and simultaneously, with the addition of a fewpreparation steps, a highly-active isomerization catalyst. These andother advantages of our invention will become apparent as the detaileddescription proceeds.

In accordance with the present invention a vapor-phase isomerizationcatalyst is prepared by the method which comprises impregnating solid,hydrous alumina containing between about 1 to 30 percent by weight ofcombined water in the presence of between about 0.001 to 0.02 mole ofaluminum chloride per mole of dry A1 0 with a solution of a platinumcompound whereby platinum is added thereto in a proportion between about0.01 and 2.0 percent by weight, based on dry A1 0 drying and calcining,impregnating the resulting composite with hy- 3,085,123 Patented Apr. 9,1963 platinic acid. The platinum may be added simultaneously Withaluminum chloride as an aqueous solution of chloroplatinic acid andaluminum chloride, or it may be added before or after the solid, hydrousalumina is contacted with aluminum chloride, preferably aqueousaluminumchloride. Prior to impregnating with hydrogen fluoride, theplatinum-containing composite is dried, e.g., at 150 to 400 F. for 0.5to 24 hours, and calcined, e.g., at 400 to 1200 F. for 0.5 to 24 hours.Hydrogen fluoride is then added, usually as aqueous hydrogen fluoride,in sufficient quantity so that the fluorine level of the resultingcomposite is in the range of about 0.5 to 5 percent by weight, based ondry A1 0 The hydrogen fluoride-impregnated composite is then exposed,before or after again being calcined, to contact with at least about 0.1percent by weight of sulfur, e.g., about 0.1 to 5 percent by Weight ofsulfur. The exposure to sulfur may be in the vapor-phase orliquid-phase, preferably in the liquid-phase. In either case thecontacted composite should then be calcined before being employed forisomerization.

When contacting the composite with sulfur in the liquid-phase, we preferto use aqueous solutions of sulfur compounds, e.g., aqueous solutions ofhydrogen sulfide, ammonium sulfide, and ammonium polysulfide. Whencontacting the composite with sulfur in the vapor-phase we may also use,in addition to hydrogen sulfide, ammonium sulfide, and ammoniumpolysulfide, other sulfur compounds such as mercaptans, carbondisulfide, and the like. As above mentioned, the catalyst should berecalcined prior to employing it for isomerization regardless of themethod of sulfur treatment. For best results, we have found that theliquid-phase treatment, followed by recalcination, is much preferred.While the sulfur treatin-g step exposes the catalyst to substantialsulfur levels, it should be understood that the subsequent calcinationremoves a substanital portion of the sulfur. The finished catalyst maythus contain only a fraction of the sulfur so added.

In accordance with the best mode contemplated, the present invention iscarried out by first preparing a platinum-alumina composite, orobtaining a platinum-alumina composite already prepared, by impregnatingsolid, hydrous alumina containing 1 to 30 percent by Weight of combinedwater in the presence of between about 0.001

to 0.02 mole of aqueous aluminum chloride per mole of dry A1 0 with anaqueous solution of chloroplatinic acid whereby the platinum is addedthereto in a proportion between 0.01 and 2 percent by weight, based ondry A1 0 After drying and calcining, the composite is impregnated withaqueous hydrogen fluoride to a fluodrogen fluoride to a fluoride levelin the range of about 0.5 to 5 percent by weight, based on dry A1 0exposing the composite to a substance selected from the group consistingof sulfur, sulfur-containing compounds, and mixtures thereof insuflicient quantity so that the catalyst is contacted with at leastabout 0.1 percent by weight of ride level of about 1.5 percent byweight, based on dry A1 0 We again dry and calcine and thereafter exposethe composite to an aqueous solution of ammonium sulfide'in sufficientquantity so that the catalyst is contacted with about 0.9 percent byweight of sulfur, based on dry A1 0 following which the catalyst isagain dried and calcined.

The resulting composite has been found to be highly selective forisomerization of paralfins, particularly the isomerization of C to Cparafiinic hydrocarbons. Effective conditions for isomerization of suchhydrocarbons with our catalyst includes a temperature in the range ofabout 500 to 800 F., preferably 550 to 750 F.; a

pressure of atmospheric or higher, e.g., atmospheric to 500 p.s.i.,preferably 50 to 250 p.s.i.; a space velocity of about 0.1 to 10,preferably 0.5 to 5.0, optimally 1.5 to 3.0; and a hydrogen rate ofabout to 10,000 standard cubic feet per barrel of hydrocarbon charge,preferably 500 i to 5,000. The catalyst has the additional advantage ofbeing readily regenerated by a simple carbon burnofi, e.g.,

Q by contacting with oxygen-containing gas at temperatures above about600 t The present invention will be more clearly understood from thespecific examples hereinafter set forth:

Example I A platinum-alumina composite was prepared by gelling, dryingand calcining a Heard-type alumina hydrosol (Heard Reissue No. 22,196,October 6, 1942) to a volatiles content of about 1 to 10 percent byweight, based on dry A1 03, and thereafter impregnating the calcinedalumina with an aqueous solution of chloroplatinic acid and aluminumchloride in sufiicient quantities so that, after again drying andcalcining, the resulting composite contained about 0.6 percent platinumand about 1.1 percent of chlorine. The resulting composite was found tobe highly effective for the'catalytic hydroforming, under well-knownreforming conditions, of full-boilingrange naphthas, having CFR-R clearoctane numbers in the range of about 35 to 70, to octane levels inexcess of about 100.

The resulting composite was thereafter tested, both before and aftertreatment in accordance with the present invention, to determine itsisomerization activity. In one experiment the composite was testedwithout any contact with hydrogen fluoride or sulfur. In a second experiment the composite was tested after being treated with aqueoushydrogen fluoride to a fluoride level of about 1.5 percent by weight,based on dry A1 following which it was dried and calcined. In a thirdexperiment the composite was tested after being contacted with anaqueous solution containing about 0.9 percent by Weight, based on dry A10 of sulfur in the form of ammonium sulfide, following which it wasdried and calcined. In the fourth experiment, which illustrates thepresent invention, the composite was tested after being treated with anaqueous hydrogen fluoride solution to a fluoride level of about 1.5percent by weight, based on dry A1 0 following which it was dried andcalcined and contacted with an aqueous solution containing 0.9 percentby weight, based on dry A1 0 of sulfur in the form of ammonium sulfideand again dried and calcined.

Each of the above catalysts were tested under isomerization conditionsincluding the particular temperatures which resulted in the maximumproduction of neohexane for that particular catalyst. Neohexane yieldwas used as one measure of activity since such component has a very highoctane number and is a highly-desirable product from an isomerizationprocess. At the same time, it is also highly desirable to minimize thecracking reactions so that charge stock, which is not isomerized, is notconverted to gas, and thus unavailable for gasoline blending and/orpossible recycle operation. Thus, maximum neohexane and minimum crackedproduct are both measures of a superior catalyst.

The isomerization activity tests were carried out utilizing a combinedmicroreactor-gas chromatography assembly similar to units described byEmmett (Paul H. Emmett, Advances in Catalysis, vol. IX, pp. 645-648,1957, Academi'c Press, Inc., Publishers, New York, NY.) and by Marchalet al. (I. Marchal, L. Convent, I. van Rysselberge, Revue de LInstitutFrancais du Ptrole 12, 1067- 1074, 1957). The reactor and chromatographcolumn were directly coupled and hydrogen carrier gas passed throughthem in series. In the operation of the unit, a small amount of charge,i.e., Z-methylpentane, was injected over a period of about 15 seconds.The injected material passed to the reactor and then to thechromatograph column-conductivity cell analyzer.

For each test the reactor was loaded with two milliliters of catalysthaving a mesh size of 4060 (ASTM Designation Ell-39). For each test thecharge stock was 2- methylpent-ane. The hydrogen carrier for the chargewas added at the rate of 40 milliliters per minute, and the total chargevolume for each test was 0.0 1 milliliter.

The chromatograph column had a diameter of A inch and a length of 12feet, and was operated at room temperature. The packing consisted ofisoquinoline on fire brick.

The neohexane yield and cracked-product yield obtained when employingeach catalyst was determined by measuring the chromatograph peak heights(in arbitrary It is readily apparent from the above table that maximumneohexane yield and minimum cracked-product yield were obtained onlywhen the catalyst was prepared in accordance with the method of thepresent invention.

Example II Another series of tests were made using five catalysts, allof which were prepared in accordance with the method of the presentinvention. For each test the fluorine and/or sulfur treat level werevaried. The same apparatus, the same charge stock, and approximately thesame conditions as in Example I were employed. 0;, yield was used as ameasure of undesired cracking and neohexane yield was used as themeasure of isomerization activity. The results are as follows:

Treating Level, Wt. Yield as Measured Percent by Chromatograph Temgi, F.

Peak Heights at ax.

Neohexane Yield Fluorine Sulfur C3 Neohexane It is apparent from theabove tabulation that in all cases a highly active isomerizationcatalyst resulted. Optimum treating levels, as measured by minimum Cyield and maximum neohexane yield were a fluorine content of 1.5 percentby weight and a sulfur-exposure level of 0.9 percent by weight.

Example III A series of twelve runs were made employing a hexane blendas the charge stock, instead of substantially pure 2- methylpentane asin Examples I and II above. The hexane blend consisted of anon-equilibrium blend of 2- methylpentane, 3-methylpentane, normalhexane, neohexane, and diisopropyl. The runs were made at varyingtemperatures with the hexane blend being charged either batch-wise orcontinuously. 'For the batchexperiments the same apparatus as inExamples I and II was employed. When the hexane blend was chargedcontinuously, the apparatus was modified so that the hydrogen stream wasfirst charged to a saturator wherein it picked up the hexane chargecontinuously.

The catalyst was prepared in accordance with the method of the presentinvention as described in Example I, except that quantities ofimpregnating and treating materials were adjusted so that the finishedcatalyst had a platinum content of about 1.2 percent, a chloride contentin excess of 2 percent, a fluoride content of about 2.5 percent, and aresidual sulfur content corresponding to a sulfur-treat level of about1.5 percent. The results are As shown in the above tabulation, in allcases equilibrium yields of neohexane and diisopropyl were obtained.When the catalyst accumulates coke, it is readily regenerated by contactwith flue gas containing about 2 percent oxygen at 700 to 1000 F.

'It is readily apparent from the above description that the presentinvention provides a catalyst which is substantially noncorrosive, has avery high isomerization ac- -tivity, can be readily regenerated, and isinexpensive to produce, particularly since it permits conversion of areforming catalyst to an isomerization catalyst.

This application is a division of application Ser. No. 774,085, filedNovember 17, 1958, now Patent No. 3,020,- 241.

Having thus described the invention, what is claimed is:

1. A hydrocarbon conversion process for isomerizing light hydrocarbonswhich comprises contacting said hydrocarbons at isomerization conditionscomprising temperatures in the range of about 500 to about 800 F.,pressures in the range of about atmospheric and about 500 p.s.i.g., andbetween about 500 to 5,000 standard cubic feet of hydrogen per barrel ofsaid hydrocarbons, with a catalyst prepared by impregnating solidhydrous alumina containing between about 1 to 30 percent by weight ofcombined water in the presence of between about 0.001 to 0.02 mole ofaluminum chloride per mole of dry A1 with a solution of a platinumcompound whereby platinum is added thereto in a proportion between about0.01 and 2.0 percent by weight, based on dry A1 0 drying and calcining,impregnating the resulting composite with hydrogen fluoride to afluoride level in the range of about 0.5 to 5 percent by weight, basedon dry A1 0 exposing the composite to a substance selected from thegroup consisting of sulfur, sulfur-containing compounds, and mixturesthereof, in sufficient quantity whereby said composite is contacted withat least about 0.1 percent by weight of sulfur, based on dry A1 0 andcalcining.

2. The process of claim 1 wherein said platinum compound is aWater-soluble chloro-platinum compound.

3. The process of claim 1 wherein said substance is an ammonium sulfide.

4. An isomerization process which comprises contacting in the vaporphase paraflinic hydrocarbons containing from about 4 to about 7 carbonatoms per molecule with a catalyst at isomerization conditionscomprising a temperature in the range of about 500 to about 800 F, apressure in the range of between about atmospheric and about 500p.s.i.g., and between about 500 to 5,000 standard cubic 'feet ofhydro-gen per barrel of said hydrocarbons, said catalyst being preparedby the method which comprises impregnating calcined alumina containingbetween about 1 to about 10 percent by weight of combined water with anaqueous solution of chloroplatinic acid and aluminum chloride, dryingand calcining the impregnated alumina, said solution being used insufficient quantity whereby after said impregnating, drying andcalcining the resulting composite contains about 0.6 weight percentplatinum and about 1.1 weight percent chlorine, based on dry A1 0treating said composite with an aqueous solution of hydrogen fluoridewhereby fluoride is added to said composite in an amount of about 1.5weight percent, based on dry A1 0 drying and calcining the resultingfluoride-containing composite, treat-ing said fluoride-containingcomposite with an aqueous solution of ammonium sulfide containing about0.9 percent by weight of sulfur, based on dry A1 0 and drying andcalcining.

No references cited.

1. A HYDROCARBON CONVERSION PROCESS FOR ISOMERIZING LIGHT HYDROCARBONSWHICH COMPRISES CONTACTING SAID HYDROCARBONS AT ISOMERIZATION CONDITIONSCOMPRISING TEMPERATURES IN THE RANGE OF ABOUT 500 TO ABOUT 800*F.,PRESSURES IN THE RANGE OF ABOUT ATMOSPHERIC AND ABOUT 500 P.S.I.G., ANDBETWEEN ABOUT 500 TO 45,000 STANDARD CUBIC FEET OF HYDROGEN PER BARRELOF SAID HYDROCARBONS, WITH A CATALYST PREPARED BY IMPREGNATING SOLIDHYDROUS ALUMINA CONTAINING BETWEEN ABOUT 1 TO 30 PERCENT BY WEIGHT OFCOMBINED WATER IN THE PRESENCE OF BETWEEN ABOUT 0.001 TO 0.02 MOLE OFALUMINUM CHLORIDE PER MOLE OF DRY AI2O3 WITH A SOLUTION OF A PLATINUMCOMPOUND WHEREBY PLATINUM IS ADDED THERETO IN A PROPORTION BETWEEN ABOUT0.01 AND 2.0 PERCENT BY WEIGHT, BASED ON DRY AI2O3, DRYING ANDCALCINING, IMPREGNATING THE RESULTING COMPOSITE WITH HYDROGEN FLUORIDETO A FLUORIDE LEVEL IN THE RANGE OF ABOUT 0.5 TO 5 PERCENT BY WEIGHT,BASED ON DRY AI2O3, EXPOSING THE COMPOSITE TO A SUBSTANCE SELECTED FROMTHE GROUP CONSISTING OF SULFUR, SULFUR-CONTAINING COMPOUNDS, ANDMIXTURES THEREOF, IN SUFFICIENT QUANTITY WHEREBY SAID CONPOSITE ISCONTACTED WITH AT LEAST ABOUT 0.1 PERCENT BY WEIGHT OF SULFUR, BASED ONDRY AI203, AND CALCINING.